Search Publications
Low-energy particle oscillations and correlations with hydromagnetic waves in the Jovian magnetosphere: Ulysses measurements
Krupp, N.; Tsurutani, B. T.; Lanzerotti, L. J. +1 more
We report on measurements of energetic particle modulations (ions and electrons with energies E>50 keV) observed by the heliosphere instrument for spectra, composition, and anisotropy at low energies (HI-SCALE) aboard the Ulysses spacecraft that were associated with the only hydromagnetic (HM) wave event measured inside the Jovian magnetosphere…
A paradigm revisited: the accretion disc in AGNs and quasars
Gondhalekar, P. M.; Kellett, B. J.; Rouillon-Foley, C.
A statistical comparison of model spectra of a thin bare accretion disc plus power-law and observations of over 400 active galactic nuclei (AGNs) and quasars are presented. This comparison is not limited to the optical/ultraviolet region of the observed spectra, as has often been the case in the past, but is extended over the entire ~4 eV to ~2 ke…
The Weak Blue Bump of H2106-099 and Active Galactic Nuclei Dereddening
Ohashi, T.; Sakao, T.; Remillard, R. A. +3 more
We present multifrequency spectra of the Seyfert 1 galaxy H2106-099, from radio to hard X-rays, spanning over a decade of observations. The hard X-ray (2-20 keV) spectrum measured with Ginga was not unusual, with a log slope (Fυ ∝ Eα), of -0.80±0.02 on 1988 May 18 and -1.02±0.10 on 1988 May 22/23 UT, and with no significant o…
Recurrent variations of anomalous oxygen in association with a corotating interaction region
Fränz, M.; Keppler, E.; Reuss, M. K.
The fluxes of anomalous oxygen (E ranging from 3.5-6.8 MeV/amu), as measured by the EPAC instrument on ULYSSES, show a recurrent variation with the solar rotation period, which is anticorrelated with the fluxes of particles accelerated at the shocks of a corotating interaction region (CIR), and correlated with the fluxes of galactic cosmic rays kn…
Voyager Observations of the Companiion of the Classical Cepheid S MUSCAE
Evans, Nancy Remage; Holberg, J. B.; Polidan, Ronalds S.
We have observed the companion of the Cepheid S Mus with the Voyager ultraviolet spectrometer, including a spectrum of the background. We have derived the energy distribution from 912 to 3200 Å using the reddening obtained from Cepheid colors corrected for the effect of the companion. This has been compared with three Morgan-Keenan "dagger" spectr…
Classification of ultraviolet stellar spectra using artificial neural networks
Gulati, R. K.; Gupta, Ranjan; Gothoskar, Pradeep +1 more
Scheme based on the artificial neural networks (ANNs) trained with multi-layer back propagation using single level network for classifying ultraviolet spectra in the IUE Low-Dispersion Spectra Reference Atlas is presented. We compare the classification results obtained from single-level network with the one from multi-level neural tree network. Bo…
ULYSSES observations of double ion beams associated with coronal mass ejections
Balogh, A.; Phillips, J. L.; Feldman, W. C. +1 more
Coronal mass ejections (CME's) are thought to result from the loss of stability within a magnetically confined coronal structure leading to its radial expansion into interplanetary space. As the CME expands into the corona current sheets will form between the expanding CME and surrounding field lines in the ambient wind. This configuration may lea…
Recent observations of the WR central star of the planetary nebula LMC-N66
Peña, Miriam; Maza, Jose; Peimbert, Manuel +2 more
The recent evolution of the central star of the planetary nebula LMC-N66 is presented. Before 1987, it showed a weak continuum with aTeff≥120 000 K andLbol≈25 000L⊙ and in a few years it developed strong WR features (P Cygni line profiles in N v at 124.0 nm and C IV at 155.0 nm, wide HeII emission, etc.) typical of…
A `Ulysses' Cosmic-Ray Latitude Gradient Observation and Modulation Models
Keppler, E.; Quenby, J. J.; Drolias, B. +2 more
The `EPAC' instrument on Ulysses is sensitive to relativistic cosmic rays when far from Jupiter and in the absence of energetic solar particles. Measurement of the latitude gradient of these particles, after correction for time variations, has been made for the 1993-1994 south polar pass. The average magnitude of the gradient is about the same or …
Astrometric positions of stars associated with nebulosities in the southern hemisphere.
Rousseau, J. M.; Perie, J. P.
Several stars associated with nebulosities and cited by S. van den Bergh and W. Herbst are included in the preliminary programme for the HIPPARCOS mission. When performing preparatory measurements of plates, we encountered difficulties in identifying certain of these objects when relying only on coordinates, which led us to take advantage of this …